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| United States Patent |
6,166,280
|
|
Rubin
, et al.
|
December 26, 2000
|
Catalyst for the dehydrogenation of ethylbenzene to styrene
Abstract
Catalysts in the form of cylindrical hollow granules, suitable for the
dehydrogenation of ethylbenzene to styrene, and comprising, as active
component, ferric oxide and promoters chosen among oxides of alkaline or
alkaline-earth metals, oxides of elements of the lanthanide series, and
chromium, tungsten, and molybdenum oxides, characterized by the absence of
macroporosities with a radius of more than 50,000 .ANG. and/or by high
mechanical characteristics of resistance to axial breaking and to
abrasion.
| Inventors:
|
Rubin; Carlo (San Fermo Della Battaglia, IT);
Cavalli; Luigi (Novara, IT);
Conca; Esterino (Novara, IT)
|
| Assignee:
|
Montecatini Technologies S.r.l. (Milan, IT)
|
| Appl. No.:
|
814191 |
| Filed:
|
March 10, 1997 |
Foreign Application Priority Data
| Mar 08, 1996[IT] | MI96A0447 |
| Current U.S. Class: |
585/445; 502/303; 502/304; 502/306; 502/316; 502/325; 502/338; 585/444 |
| Intern'l Class: |
C07C 002/64 |
| Field of Search: |
502/303,304,306,316,325,335
585/443,444,445,319,440,441
568/474
|
References Cited
U.S. Patent Documents
| 4707309 | Nov., 1987 | Voss et al. | 264/12.
|
| 5082819 | Jan., 1992 | Boeck et al.
| |
| 5330958 | Jul., 1994 | Viola et al. | 567/472.
|
| Foreign Patent Documents |
| 0 591572 | Apr., 1994 | EP.
| |
Other References
Encyclopedia of Chemical Technology, Kirk-Othmer, vol. 18, pp. 304-305,
1991.
European Search Report for EP 97 10 3427. (Jun./1997).
|
Primary Examiner: Dunn; Tom
Attorney, Agent or Firm: Cave LLP; Bruce
Claims
What is claimed is:
1. Catalysts in the form of granules having a cylindrical shape, provided
with one or more through holes which are parallel to each other and to the
axis of the granule, when more than one hole is present, having a porosity
between 0.15 and 0.35 cm.sup.3 /g and wherein, in the pore radius
distribution curve, over 50% of the pores have a radius of more than 600
.ANG. and wherein there are no macroporosities with a radius of more than
50,000 .ANG., usable in the dehydrogenation of ethylbenzene to styrene,
comprising, as active components, ferric oxide and promoters chosen among
oxides of alkaline and alkaline-earth metals, oxides of the lanthanide
series, and chromium, tungsten, and molybdenum oxides, obtained by
compression molding of powders of the promoters and of the active
components, and of precursors thereof, by using, for lubrication, as sole
lubricant, a lubricant applied to the walls of the molding chamber and to
the plungers of the mold.
2. Catalysts according to claim 1 in the form of multilobed granules with
lobes which are coaxial to the through holes.
3. Catalysts according to claim 2, provided with three holes, wherein the
ratio between the pitch of the holes and the diameter of said holes is
between 1.15 and 1.5 and the ratio between the height of the granules and
the pitch of the holes is between 1.5 and 2.5.
4. Catalysts according to claim 2 in the form of multilobed granules with
lobes which are coaxial to the axis of the holes and wherein the ratio
between the pitch of the holes and the diameter thereof is between 1.15
and 1.5 and the ratio between the height of the granules and the pitch of
the holes is between 1.5 and 2.5.
5. Catalysts according to claim 1 in the form of multilobed granules with
lobes which are coaxial to the axis of the holes and wherein the ratio
between the pitch of the holes and the diameter thereof is between 1.15
and 1.5 and the ratio between the height of the granules and the pitch of
the holes is between 1.5 and 2.5.
6. Catalysts in the form of granules having a geometric shape, provided
with one or more through holes, usable in the dehydrogenation of
ethylbenzene to styrene, and comprising, as active components, ferric
oxide and promoters chosen among oxides of alkaline and alkaline-earth
metals, oxides of the lanthanide series, and chromium, tungsten, and
molybdenum oxides, having an axial ultimate tensile strength (in the
direction of the axis of the holes) of more than 15 N/particle, said
catalysts being obtained by compression-molding of powders of the
precursor and of the active components, and of precursors thereof by
using, for lubrication, as sole lubricant, a lubricant applied to the
walls of the molding chamber and to the plungers of the mold.
7. Catalysts according to claim 6, wherein the ultimate tensile strength is
between 20 and 80 N/particle.
8. Catalysts in the form of granules having a cylindrical shape, provided
with one or more through holes which are parallel to each other and to the
axis of the granule, when more than one hole is present, usable in the
dehydrogenation of ethylbenzene to styrene, and comprising, as active
components, ferric oxide and promoters chosen among oxides of alkaline and
alkaline-earth metals, oxides of the lanthanide series, and chromium,
tungsten, and molybdenum oxides, obtained by compression molding of
powders of the active components and the promoters, and of precursors
thereof by using, for lubrication as sole lubricant, a lubricant applied
to the walls of the molding chamber and to the plungers of the mold.
9. Catalyst in the form of granules having a cylindrical shape, provided
with one or more through holes, which are parallel to each other and to
the axis of the granule, when more than one hole is present, usable in the
dehydrogenation of ethylbenzene to styrene, comprising, ferric oxide as
active component and promoters chosen among oxides of alkaline and
alkaline-earth metals, oxides of the lanthanide series, and chromium,
tungsten and molybdenum oxides, obtained by compression molding of powders
of the active components and promoters and of precursors thereof, wherein
for lubrication a lubricant is used dispersed in the bulk of the powder to
be compression molded, and the powder containing the lubricant is
heat-treated prior to the compression molding step to remove the volatile
compounds which form during the calcination step.
10. Catalysts in the form of granules having a cylindrical shape, provided
with one or more through holes which are parallel to each other and to the
axis of the granule, when more than one hole is present, usable in the
dehydrogenation of ethylbenzene to styrene, and comprising, as active
components, ferric oxide and promoters chosen among oxides of alkaline and
alkaline-earth metals, oxides of the lanthanide series and chromium,
tungsten, and molybdenum oxides, obtained by compression molding of
powders of the active components and of the precursors thereof, and
optionally of promoters, by using, for lubrication as sole lubricant, a
lubricant applied to the walls of the molding chamber and to the plungers
of the mold, and wherein one or more of the promoters and precursors
thereof are comprised in a surface layer having a thickness from 0.1 to
100 microns.
11. Process for the dehydrogenation of ethylbenzene to styrene, wherein
catalysts chosen among those according to claim 1 are used.
12. Process according to claim 11, wherein the weight ratio of
steam/ethylbenzene used in the dehydrogenation of ethylbenzene is higher
than 1.5.
Description
The present invention relates to catalysts in the form of hollow granules
having a specific geometric shape and suitable for the dehydrogenation of
ethylbenzene to styrene.
A previous and currently pending application of the Applicant discloses
catalysts having a complex geometric shape, for example a hollow
cylindrical shape with a circular or multilobed transverse cross-section
with through holes at the various lobes, obtained by compression-molding
of powders (tableting), using a lubricant applied to the walls of the
molding chamber and to the plungers of the mold for lubrication.
The resulting catalysts are characterized by constant size parameters, high
abrasion- and breakage-resistance characteristics, and very narrow pore
radius distribution. By virtue of the above mentioned type of porosity and
of the high ratio between the geometrical area and the volume of the
particles, the catalysts allow to considerably reduce the pressure drop
that occur in a fix-bed reactor and to significantly improve the activity
and selectivity of the catalyst.
BACKGROUND OF THE INVENTION
In patent literature concerning catalytic dehydrogenation of ethylbenzene
to styrene, the interest has almost always been directed towards improving
and optimizing the chemical composition in order to achieve ever more
satisfactory performances. The improvements are generally obtained by
varying the composition as regards the main components or by using
different promoters.
Limited attention has been given so far to the geometry of the catalyst.
The importance of the shape can be directly correlated to the pressure used
in the processes. Since the dehydrogenation reaction is accompanied by an
increase in volume, a pressure reduction facilitates the shifting of the
equilibrium towards the products (styrene and hydrogen), with a consequent
improvement of the conversion. The possibility of modifying the shape of
the catalyst so as to allow operation at a lower pressure (thus also
reducing the pressure drop in the catalyst bed) is therefore desirable.
Furthermore, the dehydrogenation reaction is carried out in the presence of
steam to reduce the partial pressure of styrene to shift the equilibrium
towards the formation of styrene.
In order to solve this problem, two modifications have been adopted as
regards the shape:
1) the granule diameter has been increased (to 5 mm) without altering its
length. This has solved the problem only to a very limited extent, since a
decrease in the pressure drop has indeed been achieved, owing to the
reduced bulk density (and therefore owing to an increase in the void
fraction), but at the same time the geometric surface exposed to catalysis
has decreased. The result of these two contrasting effects has been a
reduction in performance.
2) a three- or five-lobed geometric shape has been introduced. A slight
improvement has been achieved in this case. However, one should bear in
mind that the lobed shape has the drawback that powder forms more easily,
since the lobes are weaker fracture points with respect to the solid
cylindrical shape.
Industrially, the process used for catalyst shaping is extrusion molding.
It should be noted that this technologically simple process has a very
important limitation: specifically, it does not allow to obtain complex
geometric shapes, particularly hollow shapes.
As regards composition, catalysts for the dehydrogenation of ethylbenzene
to styrene comprise iron oxide, oxides of alkaline or alkaline-earth
metals, and other oxides chosen among cerium, molybdenum, tungsten, and
chromium oxide.
The life of the catalysts can be improved by adding chromium oxide as a
stabilizer. U.S. Pat. No. 3,360,597 discloses catalysts which contain
0.5-5% Cr.sub.2 O.sub.3 next to 80-90% Fe.sub.2 O.sub.3 and 9-18% K.sub.2
CO.sub.3. The catalyst is prepared according to a process which entails
the mixing in water of yellow iron oxide, chromium oxide, and potassium
carbonate so as to obtain a paste from which the catalyst is obtained in
the form of cylindrical granules by extrusion, drying, and calcination.
U.S. Pat. No. 5,023,225 discloses a catalyst for the dehydrogenation of
ethylbenzene to styrene which is based on iron oxide, oxides of alkaline
or alkaline-earth metals, and cerium, molybdenum, or tungsten oxide,
characterized in that the yellow iron oxide is blended with small amounts
of chromium oxide prior to molding the catalyst. The molding process is
characterized in that the yellow iron oxide blended with chromium oxide is
heated to 500-1000.degree. C. to be converted into red iron oxide before
mixing the components in the form of a wet paste. Molding is performed by
extrusion.
SUMMARY OF THE INVENTION
The dehydrogenation catalysts according to the invention have a hollow
geometric shape (with one or more through holes) obtained by
compression-molding (tableting) with a method in which the lubricant to be
used is not dispersed in the bulk of the powder to be formed (bulk
lubrication) but is applied to the walls of the molding chamber and to the
plungers of the mold (external lubrication). DETAILED DESCRIPTION OF THE
INVENTION
The resulting catalysts have, with respect to those prepared by using bulk
lubrication, a higher porosity, a narrower pore radius distribution, and
reduced macroporosity. Porosity is generally between 0.15 and 0.35
cm.sup.3 /g (determined by mercury absorption). The surface area is
generally between 1 and 6 m.sup.2 /g (determined by BET method). The pore
distribution curve does not include macroporosities with an average pore
radius of more than 50,000 .ANG.. More than 50% of the porosity has an
average radius of more than 600 .ANG.. More preferably, the average radius
is between 800 and 1800 .ANG..
The catalysts furthermore have constant size parameter values. Constancy of
the size parameters instead cannot be obtained with molding processes that
use internal lubrication, owing to considerable microcracks which occur on
part or all of the catalyst particle, causing embrittlement and subsequent
deformation thereof.
Because of these deformations, the compression-molding process which uses
bulk lubrication has never been used in industrial practice for the
production of hollow granular catalysts. It has furthermore been found
that the catalysts according to the invention are characterized by
mechanical properties, particularly by an axial ultimate tensile strength
(in the direction of the axis of the holes), considerably higher than
those of the corresponding catalysts obtained by bulk lubrication. The
axial ultimate tensile strength is higher than 15 N/particle and is
preferably between 20 and 80 N/particle. Abrasion-resistance is also high.
The percentage of powder is generally less than 3%. In catalysts obtained
by extrusion, abrasion-resistance is generally between 4 and 8% by weight.
The catalysts according to the invention, by virtue of the fact that they
are hollow, allow to achieve a higher conversion, for the same weight,
with respect to solid-shaped catalysts.
Furthermore, the greater presence of voids provided by these catalysts
allows to operate, for an equal fed flow-rate, at lower process pressures
than required when using solid-shaped catalysts.
The greater presence of voids allows to operate with steam/ethylbenzene
ratios higher than those usable with the catalysts having a solid shape,
thus obtaining increased conversion for an equal process pressure.
The steam/ethylbenzene weight ratio usable with the catalysts of the
invention is higher than 1.5 and can arrive to 2.5 or more.
The presence of holes allows to work with a lower wall thickness than in
solid-shaped catalysts and therefore to better use the catalytic mass. The
minimum wall thickness that can be achieved with these catalysts is
between 0.6 and 0.8 mm.
For the same weight, the catalytic mass that can be used with the catalysts
according to the invention is at least 1.5 times higher than that of
solid-shaped catalysts having a minimum diameter of 3 mm which is
compatible with the mechanical performances for practical use.
The pressure drop observed with the three-lobed catalysts according to the
invention is at least 1.3 times lower than that of solid-shaped catalysts
for an equal exposed geometric surface.
The lubricants that can be used to prepare the catalysts according to the
invention include solids and liquids capable of reducing the friction
coefficient between the powder to be tableted and the parts of the
tableter that make contact with said powder.
Examples of suitable lubricants are stearic acid and palmitic acid;
alkaline and alkaline-earth salts of these acids, such as magnesium and
potassium stearate; carbon black, talc, mono- and triglycerides such as
glycerol monostearate and glycerol mono-oleate, paraffin oil, and
perfluoropolyethers.
The liquid lubricants can be used as solutions or as disperse systems in
dispersants.
The amount of liquid lubricant is generally between 0.025 and 25 mg per
granule.
The solid lubricants can be applied by dusting the forming chamber and the
plungers, that is to say, by covering them with a thin layer of lubricant
powder conveyed continuously by a stream of air or other gas so as to
achieve optimum dispersion of the solid.
The molding chamber and the plungers can be made of, or coated with,
self-lubricating materials, such as polytetrafluoroethylene or ceramic
material. This allows to avoid or reduce the use of lubricant.
The catalysts according to the invention preferably have a hollow
cylindrical shape with one or more through holes. In the case of catalysts
with two or more through holes, the axes are substantially parallel to
each other and to the axis of the granule and are substantially mutually
lo equidistant.
Preferably, the through holes have a circular cross-section. In the case of
catalysts with three through holes, the axes form, relative to the
transverse cross-section of the particle, the corners of a substantially
equilateral triangle; said corners are orientated towards the points where
the transverse cross-section makes contact with the circumscribed
circumference. The lobes are preferably cylindrical and circular,
identical to each other, and coaxial to the through holes.
The granules may also have a substantially triangular transverse
cross-section with rounded corners.
The ratio between the pitch of the holes (i.e., the distance between their
respective axes) and the diameter of said holes is preferably between 1.15
and 1.5 and more preferably between 1.3 and 1.4.
The ratio between the height of the particle and the pitch of the holes is
preferably between 1.5 and 2.5 and more preferably between 1.7 and 2.3.
In the case of catalysts having a circular transverse cross-section, the
ratio between the radius of curvature of each lobe and the pitch of the
holes is preferably between 0.6 and 0.9, more preferably between 0.7 and
0.8. The ratio between the radius of curvature of the lobes and the radius
of the through holes is preferably between 1.3 and 2.7, more preferably
between 1.8 and 2.10. The ratio between the radius of the circle
circumscribed about the transverse cross-section and the radius of
curvature of the circular lobes is preferably between 1.6 and 2, more
preferably between 1.7 and 1.85. The surface-to-volume ratio of each
granule in the multilobed version is preferably higher than 2.0 and more
preferably higher than 2.2.
In the case of catalysts having a triangular transverse cross-section, the
ratio between the radius of curvature of each rounded corner and the pitch
of the holes is preferably between 0.6 and 0.9 and more preferably between
0.7 and 0.8. The ratio between the radius of the circle circumscribed to
the transverse cross-section and the radius of curvature of each rounded
corner is preferably between 1.6 and 2, more preferably between 1.7 and
1.85. The surface-to-volume ratio of each granule, in the version having a
triangular cross-section, is preferably higher than 2.0, more preferably
higher than 2.2.
In preparing the catalysts according to the invention, the powder
containing the precursors and/or active components of the catalyst is
dry-mixed or blended with the addition of a small amount of water to
obtain a mixture that contains uniformly distributed components.
The resulting mixture is subjected to a drying and/or calcining cycle at
temperatures between 120 and 1000.degree. C. for a time that is sufficient
to remove the water and the volatile decomposition products.
The pressure used is generally higher than 100 kg/cm.sup.2 nd can reach
1000 kg/cm.sup.2 or more.
It has furthermore been found, and this constitutes a further aspect of the
present invention, that catalysts with mechanical characteristics,
particularly axial ultimate tensile strength, which fall within those of
the catalysts that can be obtained by molding with external lubrication
can also be achieved by shaping using bulk lubrication, provided that the
powder, prior to shaping, is subjected to heat treatments capable of
ensuring that the decomposition reactions which occur with weight loss
take place before the molding step. In this case, the internal lubricant
is used in an amount that is less than 5% by weight.
The resulting powder is suitable for preparing granules of the desired
shape and size, using the method of compression-molding.
After molding, the granules are calcined at 600-900.degree. C.
The promoters and stabilizers, such as calcium, magnesium, chromium,
molybdenum, and tungsten oxide, can be distributed within the mass of the
granule or on its surface. Various methods can be used to provide the
surface deposition of the desired components. For example, the component
or components can be sprayed onto the granules during tableting after the
external lubrication step.
It is furthermore possible to use a lubricant which acts as precursor of
the desired compound, for example stearates of alkaline and alkaline-earth
metals.
These compounds, after calcination, are converted into the corresponding
oxides or mixed oxides or salts.
It is possible to use other mixtures of lubricants and oxides or other
catalytically active compounds and spray a thin layer onto the surface of
the granules during molding.
As an alternative, it is possible to coat the catalyst granules with a thin
layer by working in a stage that is separate from tableting and occurs
after it. According to a preferred method, the catalyst granules at the
output of the calcination stage are struck, while heated to the
temperature of 80-200.degree. C., by a solution or dispersion of the
promoter and stabilizing oxides or salts of metals by means of a
nebulizer. The concentration of the dispersion, the contact time, and the
temperature at which deposition is performed can be changed so as to
ensure quick and complete evaporation of the water or other dispersant
fluid, in order to form a surface layer having a desired thickness,
generally between 0.1 and 100 microns.
In terms of final composition by weight, expressed as oxides, the catalysts
comprise 50-92% ferric oxide, 5-20% alkaline metal oxide, 0.5-14%
alkaline-earth metal oxide, 2-10% oxide of elements of the lanthanide
series, 0.5-6% oxide of a metal of the sixth group of the periodic table.
Potassium oxide is preferred among oxides of alkaline metals, whilst
magnesium and calcium oxides are preferred among alkaline-earth ones.
Cerium oxide is preferred among lanthanide-series oxides, and molybdenum
and tungsten oxides are preferred among group VI oxides.
It is possible to use for example ferric hydroxide, ferric nitrate or
carbonate, potassium hydroxide or carbonate, cerium carbonate, or ammonium
molybdate as precursors of the active components.
A representative but non-limitative composition-is as follows, expressed as
oxides by weight percentages:
Fe.sub.2 O.sub.3 =78%; K.sub.2 O=12%; CeO.sub.2 =5%; Mg=2%; WO.sub.3 =0.9%;
MoO.sub.3 =2.1%
Another representative composition, again expressed as a percentage of
oxides by weight, is:
Fe.sub.2 O.sub.3 =74%; K.sub.2 O=6%; CeO.sub.2 =10%; MgO=4%; WO.sub.3 =6%
The catalysts having a non-uniform composition, obtained by surface
deposition of promoter and stabilizing components on the granules, contain
40-95% iron oxide, 5-30% alkaline metal oxide, 0.05-4% alkaline-earth
metal oxide, 0.1-10% oxide of an element of the lanthanide series, 0.05-4%
chromium, molybdenum, or tungsten oxide.
In particular, potassium oxide, calcium oxide, magnesium oxide, cerium
oxide, and chromium, molybdenum, and tungsten oxides are preferred next to
iron oxide.
Examples of preferred but non-limitative compositions are listed hereafter.
The asterisk indicates the component that can be deposited on the surface.
______________________________________
% % % % % % % %
Fe.sub.2 O.sub.3 K.sub.2 O CeO.sub.2 MgO CaO Cr.sub.2 O.sub.3 MoO.sub.3
WO.sub.3
______________________________________
78 12 5 2 0.09* / 2.1 0.9
78 14 5 0.1* / / 2 0.9
74.5 16.1 9.6 4.0 / / / 5.8
78 12 5 2.9 / / 2 0.1*
78 12 5 4 / / 0.1* 0.9
78 14 5 2.8 / / 0.1* 0.1*
78 12 5 4.6 / 0.1* 0.1* 0.1*
0.1*
______________________________________
The reaction for the dehydrogenation of ethylbenzene to styrene is usually
performed at 540 to 650.degree. C. at pressures which are higher, lower,
or equal to the atmospheric pressure. Low pressures are preferred due to
thermodynamic reasons, since they allow higher conversions for an equal
temperature.
The following examples are provided to illustrate and not to limit the
invention.
Analytical determinations
The axial ultimate tensile strength was determined according to ASTM D
4179/82; apparent density (tapped) was determined according to ASTM D
4164/82.
COMPARISON EXAMPLE 1
A paste was prepared by mixing hydrated ferric oxide, cerium carbonate,
magnesium carbonate, and tungsten oxide with an aqueous solution of
potassium hydroxide, so as to obtain a final catalytic product having the
following composition (expressed in % of oxides by weight).
______________________________________
Oxides
%
______________________________________
Fe.sub.2 O.sub.3
76.1
K.sub.2 O 14.0
CeO.sub.2 6.5
MgO 2.5
WO.sub.3 0.9
______________________________________
The paste was extruded to form granules with a length of 5 mm and a
diameter of 3.5 mm. The extruded granules were dried at 150.degree. C. for
16 hours and then calcined at 400.degree. C. for 2 hours. Some of the
granules were calcined at 700.degree. C. for 2 hours. These granules
constitute the catalyst 1.
EXAMPLE 1
A second part of the granules prepared according to comparison Example 1
was ground and the powder was tableted, using stearic acid as external
lubricant. The plunger and the cylindrical chamber of the tableter were
coated with a thin layer of stearic acid, carried continuously by an air
stream. Cylinders 4 mm long, with a through hole having a diameter of 2
mm, were tableted. The pressure used was 500 kg/cm.sup.2. The cylindrical
granules were calcined at 700.degree. C. for 2 hours.
This is catalyst no. 2. The axial ultimate tensile strength of this
catalyst was 13.4 N/particle.
EXAMPLE 2
A second part of the granules prepared according to comparison Example 1
was ground and tableted (with external lubrication using stearic acid) in
a three-lobed shape with three parallel through holes having an inside
diameter of 1.3 mm, with a wall thickness of 0.8 mm, a circumference
radius of 2.5 mm, and a height of 5 mm. The holes were located at the
corners of an equilateral triangle. The tablets were calcined at
700.degree. C. for 2 hours.
This is catalyst no. 3. The axial ultimate tensile strength of this
catalyst was 20.9 N/particle.
EXAMPLE 3
A catalyst having the following composition by weight, expressed as oxides,
was prepared with the method of comparison Example 1:
Fe.sub.2 O.sub.3 =74.5%; K.sub.2 O=6.1%; CeO.sub.2 =9.6%; MgO=4.0%;
WO.sub.3 =5.8%
Fe.sub.2 O.sub.3 in the red spheroidal form was used as Fe.sub.2 O.sub.3.
K.sub.2 O as introduced as KOH.
Calcination was performed at 800.degree. C. for 4 hours.
This is catalyst no. 4.
EXAMPLE 4
Part of the granules prepared according to Example 3 was ground and
tableted according to the method of Example 2 so as to obtain three-lobed
granules with three holes, having the characteristics specified in Example
2.
Mg stearate was used instead of stearic acid as external lubricant.
The axial ultimate tensile strength of this catalyst was 32 N/particle; 38%
of the volume was formed by pores having a radius of 600 to 800 .ANG., 11%
by pores having a radius of 800 to 1000 .ANG., 12% by pores having a
radius of 1000 to 2000 .ANG., and 6% by pores having a radius of 2000 to
4000 .ANG..
There were no macroporosities with a radius of more than 50000 .ANG..
The surface area of the catalyst was 4.9 m.sup.2 /g; porosity was 0.17
ml/g.
This is catalyst no. 5.
EXAMPLE 5
Catalysts no. 1, 2, 3, 4, and 5 were tested in a steel reactor with an
inside diameter of 35 mm. In each test, 200 cm.sup.3 of catalyst were
placed in the reactor and supported with a steel grille. Tests at
570.degree., 590.degree., and 610.degree. C. were conducted for each
catalyst; in these tests, water vapor and ethylbenzene, preheated to the
above temperatures, were passed through the catalytic bed with a
water/ethylbenzene ratio of 2.4 by weight; the output pressure was 1.05
atm and the hourly spatial velocity of the ethylbenzene was 0.5. Samples
of the reaction products were collected over 2 hours after the system had
been stabilized for at least 20 hours for each condition. The percentages
of conversion and molar selectivity are listed in the following table.
TABLE 1
______________________________________
Temperature(.degree. C.)
Conversion %
Selectivity %
______________________________________
Cat. 1 570 50.31 93.3
BD = 1.08 590 62.47 91.34
610 74.62 88.05
Cat. 2 570 54.66 93.34
BD = 1.01 590 64.85 91.52
610 75.34 88.73
Cat. 3 570 55.12 93.53
BD = 0.857 590 65.43 91.70
610 76.17 89.08
Cat. 4 570 60 88
BD = 1.42
Cat. 5 570 60 90.5
BD = 1.08
______________________________________
BD = apparent density in g/ml.
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